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  <div class="question_difficulty">
   难度：Medium
  </div>
  <div>
   <h1 class="question_title">
    537. Complex Number Multiplication
   </h1>
   <p>
    Given two strings representing two
    <a href="https://en.wikipedia.org/wiki/Complex_number">
     complex numbers
    </a>
    .
   </p>
   <p>
    You need to return a string representing their multiplication. Note i
    <sup>
     2
    </sup>
    = -1 according to the definition.
   </p>
   <p>
    <b>
     Example 1:
    </b>
    <br>
   </p>
   <pre>
<b>Input:</b> "1+1i", "1+1i"
<b>Output:</b> "0+2i"
<b>Explanation:</b> (1 + i) * (1 + i) = 1 + i<sup>2</sup> + 2 * i = 2i, and you need convert it to the form of 0+2i.
</pre>
   <p>
    <b>
     Example 2:
    </b>
    <br>
   </p>
   <pre>
<b>Input:</b> "1+-1i", "1+-1i"
<b>Output:</b> "0+-2i"
<b>Explanation:</b> (1 - i) * (1 - i) = 1 + i<sup>2</sup> - 2 * i = -2i, and you need convert it to the form of 0+-2i.
</pre>
   <p>
    <b>
     Note:
    </b>
   </p>
   <ol>
    <li>
     The input strings will not have extra blank.
    </li>
    <li>
     The input strings will be given in the form of
     <b>
      a+bi
     </b>
     , where the integer
     <b>
      a
     </b>
     and
     <b>
      b
     </b>
     will both belong to the range of [-100, 100]. And
     <b>
      the output should be also in this form
     </b>
     .
    </li>
   </ol>
  </div>
  <div>
   <h1 class="question_title">
    537. 复数乘法
   </h1>
   <p>
    给定两个表示
    <a href="https://baike.baidu.com/item/%E5%A4%8D%E6%95%B0/254365?fr=aladdin">
     复数
    </a>
    的字符串。
   </p>
   <p>
    返回表示它们乘积的字符串。注意，根据定义 i
    <sup>
     2
    </sup>
    = -1 。
   </p>
   <p>
    <strong>
     示例 1:
    </strong>
   </p>
   <pre>
<strong>输入:</strong> "1+1i", "1+1i"
<strong>输出:</strong> "0+2i"
<strong>解释:</strong> (1 + i) * (1 + i) = 1 + i<sup>2</sup> + 2 * i = 2i ，你需要将它转换为 0+2i 的形式。
</pre>
   <p>
    <strong>
     示例 2:
    </strong>
   </p>
   <pre>
<strong>输入:</strong> "1+-1i", "1+-1i"
<strong>输出:</strong> "0+-2i"
<strong>解释:</strong> (1 - i) * (1 - i) = 1 + i<sup>2</sup> - 2 * i = -2i ，你需要将它转换为 0+-2i 的形式。 
</pre>
   <p>
    <strong>
     注意:
    </strong>
   </p>
   <ol>
    <li>
     输入字符串不包含额外的空格。
    </li>
    <li>
     输入字符串将以&nbsp;
     <strong>
      a+bi
     </strong>
     的形式给出，其中整数
     <strong>
      a
     </strong>
     和
     <strong>
      b
     </strong>
     的范围均在 [-100, 100] 之间。
     <strong>
      输出也应当符合这种形式
     </strong>
     。
    </li>
   </ol>
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